[132.03] The Effect of MHD Winds on Trans-Alfvénic Jets

P.E. Hardee (U. Alabama), A. Rosen (Armagh Obs.)

Jets in protostellar systems and jets in AGN may be
surrounded by a more slowly moving magnetized wind.
Theoretical analysis and numerical simulations of 3D MHD
jets reveal that destabilization of these jets by the
Kelvin-Helmholtz instability can be delayed considerably by
the presence of a relatively modest magnetized wind flow
outside the more highly collimated jet flow. In the absence
of a wind a ``light'' jet destabilizes abruptly to helical
and other non-axisymmetric modes of distortion at the
Alfvén point transition from sub- to super-Alfvénic
flow. The wind flow can stabilize or significantly reduce
the growth rate of non-axisymmetric jet distortion to
locations well beyond the Alfvén point. The unstable
axisymmetric pinch mode distortion remains much less
influenced by an external wind and can be the dominant
unstable mode. Thus, we find a mechanism that could produce
knots in the flow without accompanying destructive
non-axisymmetric jet distortions.

Supported by the National Science Foundation through grant
AST-9802955 to the University of Alabama.